3 EXCEDE PROJECT ORGANIZATIONEXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLOREREXCEDE PROJECT ORGANIZATIONAll major project partners are members of a single integrated team. The EXCEDE project optimally combines astronomers, astrophysicists, and theorists engaged in studying and modeling circumstellar planet-forming environments, exoplanetary systems and their architectures, with leading experts in cutting-edge observational methodology and instrumentation, and highly experienced spacecraft engineering, development and mission operations teams. The EXCEDE project members and their institutions have the demonstrated experience to provide groundbreaking science with low risk while meeting the cost and schedule. Each of the partners has worked with the others in successfully delivering on NASA projects.

6 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERCS Disks: Signposts of Planetary Systems & Tracers of PlanetsThe mere presence of a debris disk is a signpost for some sort of planetary system.Spatially resolved imaging reveals its structure and traces the presence of massive planets.EXCEDE WILL UTILIZE OBSERVATIONS OF DUSTY CS DISKS TO:1. Explore the amount of dust in Habitable Zones (where dust indirectly traces the level of terrestrial planet bombardment by asteroids and meteorids).2. Help determine if this dust will interfere with future planet-finding missions.3. Constrain the composition of material delivered to planets.4. Investigate what fraction of systems have massive planets on large orbits.5. Observe how protoplanetary disks make Solar System-like architectures.6. Measure the reflectivity of giant planets and constrain their compositions.

8 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERUsing Disks to Discover the Diversity of Planetary SystemsNearly 400 CS disks have been identified by excess thermal emission.Spatially resolved images have been secured for < 5% of these disks.The small number of CS disksthat have been imaged showa remarkable diversity in disk architectures.Interpreting SEDs withoutsuch images provides only ambiguous informationabout disk structures.Spatially resolved imagesare required to reveal the structures of CS disks and their planetary systems.• Similar SEDs but very different image morphologies.• Small grains radiate less efficiently than large.• At a given equilibrium temperature, small grainsreside at greater stellocentric distances.

9 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERUsing Disks to Discover the Diversity of Planetary SystemsScattered-light images provide the greatest insights because they trace dust at a wide range of stellocentric distances, but…No existing coronagraphs have sufficiently small inner working angles and disk-to-star image contrast sensitivity to probe CS disk systems.in their habitable zones (where the Earth resides in our solar system).Dynamical interactions between planets and disks are predicted toplay vital roles in generating the architectures of planetary systems,but the inner regions of such systems, today, remain obscured.HST optical images of CS Disks. EXCEDE will image ~ 1000x fainter in contrast and at least 3xcloser to their stars and at spatial resolutions comparable to the best JWST will deliver.

10 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERS.O. 1: What are the levels of dust in the HZs of exoplanetary systems?EXCEDE will provide direct images of scattered light debris disks around a sample of ~ 230 nearby (< 100 pc) stars revealing the levels of zodiacal light (ZL) present in these systems.EXCEDE imagery will probe far interior to the Kuiper belt regions of nearby stars, into the now-elusive terrestrial planet and habitable zones of these dusty planetary systems, providing evidence for asteroid belts, comets and unseen planets.ZL is a proxy for:The richness of planetesimal belts and their degree of gravitational stirring.(b) indirect indication of the level of the bombardment that might be experienced by terrestrial planets in these systems.For > ¼ our DD target sample, EXCEDE’s 0.14” IWA enables spatially resolved imaging in CS HZs — where liquid water can exist on planetary surfaces.

11 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERS.O. 2: Will dust in the HZs interfere with planet-finding?The amount of dust in HZs is critical in determining the best strategiesto image Earth-like exoplanets — Dust-scattered starlight is the main source of astrophysical “noise” in detecting such faint point sources.But… It is conceivable that by targeting stars without debris dust, future exoplanet imaging missions may be selecting targets unlikely to have had sufficient initial mass for rich planetary systems (?)

12 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERS.O. 3: What veneer is delivered to planets by asteroids and comets?Identifying the presence of icy and organic-rich disk grains will give the first clues to the presence of volatiles important for life. EXCEDE’s two-band imaging polarimeter is crucial to disentangling the dynamical and compositional history of disks.Distinguishing Grain Properties 2-Band PolarimetryDifferent grains types (e.g.: ISM-like, solid; moderate size fluffy grains, dotted; larger grains, dashed) have different l dependent opacity (k) and scattering efficiencies (w), directional profiles (g) and degree of polarization (DoP).EXCEDE measures the DoP of dust-scattered starlight as a stellocentric function of azimuthal angle.HST prototype coronagraphic polarimetry observations of the very bright AB Aur CS disk place tight constraints on the likely composition of the light-scattering dust in this system. EXCEDE will probe many more CS disks in this way.Disks may be full of volatile-rich porous grains that carry H2O and C, , or compact and bone-dry spherules, to planet surfaces.AB AurigaePerrin et al. 2009•Disks may be full of volatile-rich porous grains that carry H2O and C to planet surfaces, or compact and bone-dry spherules. Different grains have different l dependent absorption (k) and scattering efficiencies (w), directional profiles (g) and degree of polarization (DoP). Examples show compact ISM-like grains (solid lines), moderate-sized fluffy grains (dotted) and larger grains (dashed) as in some PP disks.•EXCEDE measures the DoP of dust-scattered starlight as a stellocentric function of azimuthal angle. HST prototype coronagraphic polarimetry observations of the very bright AB Aur CS disk (accessible at HST contrasts) place tight constraints on the likely composition of the light-scattering dust in this system. EXCEDE will probe many more CS disks in this way.

13 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERS.O. 4: How many systems have massive planets on large orbits?EXCEDE’s image contrast and 144 mas spatial resolution (e.g., pc) will vastly increase the number of Neptune-analogs discovered from dynamical influences on debris disks.Structure in disks betrays the presence of planetary systems. EXCEDE will reveal the radial locations of planetesimal belts — a powerful indicator of gas-giant and ice-giant planets.AB AurigaePerrin et al. 2009

14 EXCEDE — EXOPLANETARY CIRCUMSTELLAR ENVIRONMENTS and DISK EXPLORERS.O. 5: How do PP disks make Solar-System-like architectures?6EXCEDE images will reveal disk sub-structures including large (> 20 AU) cavities and gaps associated with young Jovian-mass images.EXCEDE will observationally test models that predict gaps opening in CS disks as a result of tidal interactions with giant planets..Theoretical models predict material-depleted disk “gaps” evolving over time due to the presence of co-orbiting planets (E.g., above from Bryden et. al 1999).AB AurigaePerrin et al. 2009